1. Field of the Invention
The present invention relates to a hydraulic control device for an automatic transmission.
2. Related Background Art
Hitherto, there has been known a hydraulic control device for an automatic transmission provided with a regulator valve which is configured to regulate a line pressure to be supplied freely to an engagement element and a linear solenoid valve which is configured to regulate a line pressure for adjusting an opening degree of the regulator valve and supply it to one end of the regulator valve (for example, refer to Japanese Patent Laid-open No. 2005-90665). Moreover, there has been known as well a device which is configured to supply an output oil pressure from the linear solenoid valve directly to the engagement element.
In the conventional hydraulic control device, in coping with plural oil pressures, the maximum output oil pressure from the linear solenoid valve is preliminarily set at the highest necessary oil pressure. When engaging the engagement element at a low necessary oil pressure, a driving electric current is controlled so as to give an appropriate output oil pressure. However, since the control range of electric current for regulating the necessary oil pressure to a low pressure is narrow, there arises a problem that the controllability of the output oil pressure for engaging the engagement element is not good.